This invention relates to the formation of hermetic seals and more particularly to a method for achieving hermetic seals between two metallic portions of a battery container by employing redundant welds.
Newer forms of batteries, both primary and secondary, develop high voltages and high energy densities by employment of very reactive materials such as lithium. Some even employ reactive cathode electrolytes such as thionyl chloride. Packaging for such materials must have a high degree of reliability since the materials are dangerous and even toxic under many conditions. Accordingly, hermeticity requirements have led to the use of metal cans for such batteries, the cans being welded together. However, when such batteries employ reactive and volatile ingredients like thionyl chloride, simple welding is found to be ineffective. The high pervasiveness of thionyl chloride allows it to leak through even microscopic weld inadequecies.